Methods and apparatus for forming rhodium-containing layers

ABSTRACT

A method of forming a rhodium-containing layer on a substrate, such as a semiconductor wafer, using complexes of the formula L y RhY z  is provided. Also provided is a chemical vapor co-deposited platinum-rhodium alloy barriers and electrodes for cell dielectrics for integrated circuits, particularly for DRAM cell capacitors. The alloy barriers protect surrounding materials from oxidation during oxidative recrystallization steps and protect cell dielectrics from loss of oxygen during high temperature processing steps. Also provided are methods for CVD co-deposition of platinum-rhodium alloy diffusion barriers.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional patent application of Ser. No.09/651,699, Confirmation No. 2475, filed on Aug. 30, 2000 now U.S. Pat.No. 6,690,055, entitled DEVICES CONTAINING PLATINUM-RHODIUM LAYERS ANDMETHODS, which is a divisional of U.S. patent application Ser. No.09/146,556, filed Sep. 3, 1998, issued as U.S. Pat. No. 6,271,131 onAug. 7, 2001, which is a Continuation-in-Part of U.S. patent applicationSer. No. 09/140,921, filed on Aug. 26, 1998 (abandoned).

FIELD OF THE INVENTION

The invention relates generally to integrated circuits and moreparticularly to the use of platinum-rhodium (Pt—Rh) alloy materials forelectrodes and diffusion barrier layers to protect cell dielectrics insuch circuits. The invention further relates generally to thepreparation of rhodium-containing layers on substrates, particularly onsemiconductor device structures.

BACKGROUND OF THE INVENTION

Layers of metals and metal oxides, particularly the heavier elements ofGroup VIII, are becoming important for a variety of electronic andelectrochemical applications. For example, high quality RuO₂ thin filmsdeposited on silicon wafers have recently gained interest for use inferroelectric memories. Many of the Group VIII metal layers aregenerally unreactive toward silicon and metal oxides, resistant todiffusion of oxygen and silicon, and are good conductors. Oxides ofcertain of these metals also possess these properties, although perhapsto a different extent.

Thus, layers of Group VIII metals and metal oxides, particularly thesecond and third row metals (e.g., Ru, Os, Rh, Ir, Pd, and Pt) havesuitable properties for a variety of uses in integrated circuits. Forexample, they can be used in integrated circuits for electricalcontacts. They are particularly suitable for use as barrier layersbetween the dielectric material and the silicon substrate in memorydevices, such as ferroelectric memories. Furthermore, they may even besuitable as the plate (i.e., electrode) itself in capacitors. Rhodium isof particular interest because it is one of a few elements having aresistivity of less than 5 μΩ-cm (resistivity at 20° C. 5=4.51 μΩ-cm).

Capacitors are used in a wide variety of integrated circuits. Capacitorsare of special concern in DRAM (dynamic random access memory) circuits;therefore, the invention will be discussed in connection with DRAMmemory circuits. However, the invention has broader applicability and isnot limited to DRAM memory circuits. It may be used in other types ofmemory circuits, such as SRAMs, as well as any other circuit in whichcell dielectrics are used.

There is continuous pressure in the industry to decrease the size ofindividual cells and increase memory cell density to allow more memoryto be squeezed onto a single memory chip. However, it is necessary tomaintain a sufficiently high storage capacitance to maintain a charge atthe refresh rates currently in use even as cell size continues toshrink. This requirement has led DRAM manufacturers to turn to threedimensional capacitor designs, including trench and stacked capacitors.Stacked capacitors are capacitors which are formed over the accesstransistor in a semiconductor device. In contrast, trench capacitors areformed in the wafer substrate beneath the transistor. For reasonsincluding ease of fabrication and increased capacitance, mostmanufacturers of DRAMs larger than 4 Megabits use stacked capacitors.Therefore, the present invention will be discussed in connection withstacked capacitors, but should not be understood to be limited thereto.

One widely used type of stacked capacitor is known as a containercapacitor. Known container capacitors are in the shape of an upstandingtube (cylinder) with an oval or circular cross section. The wall of thetube consists of two electrodes, i.e., two plates of conductivematerial, such as doped polycrystalline silicon (referred to herein aspolysilicon or poly), separated by a dielectric, such as tantalumpentoxide (Ta₂O₅). The bottom end of the tube is closed, with the outerwall in contact with either the drain of the access transistor or a plugwhich itself is in contact with the drain. The other end of the tube isopen. The sidewall and closed end of the tube form a container; hencethe name “container capacitor.”

The electrodes in a DRAM cell capacitor must protect the dielectriclayer from interaction with surrounding materials, including interlayerdielectrics (e.g., BPSG), and from the harsh thermal processingencountered in subsequent steps of DRAM process flow. In order tofunction well as a bottom electrode, the electrode layer or layer stackmust act as an effective barrier to the diffusion of oxygen and silicon.Oxidation of the underlying Si will result in decreased seriescapacitance, thus degrading the cell capacitor. Platinum is one of thecandidates for use as an electrode material for high dielectriccapacitors. Platinum, alone, however, is relatively permeable to oxygen.One solution is to alloy the Pt with Rh to enhance the barrierproperties of the layer. Physical vapor deposition (PVD) of a Pt—Rhalloy has been shown by H. D. Bhatt et. al., “Novel high temperaturemulti-layer electrode barrier structure for high-density ferroelectricmemories,” Applied Physics Letters, 71, pp. 719-21 (1997), to provide animprovement over pure Pt for electrode applications. However, PVDdeposition does not deliver a layer which is sufficiently conformal forVLSI devices.

Thus, there is a continuing need for methods and materials for thedeposition of metal-containing layers, such as rhodium-containinglayers, which can function as barrier layers, for example, in integratedcircuits. Furthermore, what is needed are capacitor electrodes, barrierlayers, and fabrication methods that offer a combination of goodconformality, high conductivity, and good barrier properties.

SUMMARY OF THE INVENTION

The present invention is directed to methods for manufacturing asemiconductor device that involve forming a rhodium-containing layer onsubstrates, such as semiconductor substrates or substrate assembliesduring the manufacture of semiconductor structures. Therhodium-containing layer can be a pure rhodium layer, a rhodium oxidelayer, a rhodium sulfide layer, a rhodium selenide layer, a rhodiumnitride layer, a rhodium alloy layer, or the like. Typically andpreferably, the rhodium-containing layer is electrically conductive. Theresultant layer can be used as a barrier layer or electrode in anintegrated circuit structure, particularly in a memory device such as aDRAM device.

The metal-containing layer can include pure rhodium, or a rhodium alloycontaining rhodium and one or more other metals (including transitionmetals, main group metals, lanthamides) or metalloids from other groupsin the Periodic Chart, such as Si, Ge, Sn, Pb, Bi, etc. Furthermore, forcertain preferred embodiments, the metal-containing layer can be anoxide, nitride, sulfide, selenide, telluride, or combinations thereof.

Thus, in the context of the present invention, the term“metal-containing layer” includes, for example, relatively pure layersof rhodium, alloys of rhodium with other Group VIII transition metalssuch as iridium, nickel, palladium, platinum, iron, ruthenium, andosmium, metals other than those in Group VIII, metalloids (e.g., Si), ormixtures thereof. The term also includes complexes of rhodium or rhodiumalloys with other elements (e.g., O, N, and S). The terms “singletransition metal layer” or “single metal layer” refer to relatively purelayers of rhodium. The terms “transition metal alloy layer” or “metalalloy layer” refer to layers of rhodium in alloys with other metals ormetalloids, for example.

One preferred method of the present invention involves forming a layeron a substrate, such as a semiconductor substrate or substrate assemblyduring the manufacture of a semiconductor structure. The methodincludes: providing a substrate (preferably, a semiconductor substrateor substrate assembly); providing a precursor composition comprising oneor more complexes of the formula:L_(y)RhY_(z),  (Formula I)wherein: each L group is independently a neutral or anionic ligand; eachY group is independently a pi bonding ligand selected from the group ofCO, NO, CN, CS, N₂, PX₃, PR₃, P(OR)₃, AsX₃, AsR₃, As(OR)₃, SbX₃, SbR₃,Sb(OR)₃, NH_(x)R_(3-x), CNR, and RCN, wherein R is an organic group andX is a halide; y=1 to 4; z=0 to 4 (preferably, 1 to 4); x=0 to 3;providing a nonhydrogen reaction gas; and forming a metal-containinglayer from the precursor composition in the presence of the nonhydrogenreaction gas on a surface of the substrate (preferably, thesemiconductor substrate or substrate assembly). The metal-containinglayer can be a single transition metal layer or a transition metal alloylayer, for example. Using such methods, the complexes of Formula I areconverted in some manner (e.g., decomposed thermally) and deposited on asurface to form a metal-containing layer. Thus, the layer is not simplya layer of the complex of Formula I.

Complexes of Formula I are neutral complexes and may be liquids orsolids at room temperature. Typically, however, they are liquids. Ifthey are solids, they are preferably sufficiently soluble in an organicsolvent or have melting points below their decomposition temperaturessuch that they can be used in various vaporization techniques, such asflash vaporization, bubbling, microdroplet formation, etc. However, theymay also be sufficiently volatile that they can be vaporized or sublimedfrom the solid state using known chemical vapor deposition techniques.Thus, the precursor compositions of the present invention can be insolid or liquid form. As used herein, “liquid” refers to a solution or aneat liquid (a liquid at room temperature or a solid at room temperaturethat melts at an elevated temperature). As used herein, a “solution”does not require complete solubility of the solid; rather, the solutionmay have some undissolved material, preferably, however, there is asufficient amount of the material that can be carried by the organicsolvent into the vapor phase for chemical vapor deposition processing.

Yet another method of forming a metal-containing layer on a substrate,such as a semiconductor substrate or substrate assembly during themanufacture of a semiconductor structure, involves: providing asubstrate (preferably, a semiconductor substrate or substrate assembly);providing a precursor composition comprising one or more organicsolvents and one or more precursor complexes of Formula I as definedabove; providing a nonhydrogen reaction gas, preferably an oxidizinggas; vaporizing the precursor composition to form vaporized precursorcomposition; and directing the vaporized precursor composition towardthe substrate to form a metal-containing layer in the presence of anonhydrogen reaction as on a surface of the substrate. Herein, vaporizedprecursor composition includes vaporized molecules of precursorcomplexes of Formula I either alone or optionally with vaporizedmolecules of other compounds in the precursor composition, includingsolvent molecules, if used.

Still another method of forming a layer on a substrate involves:providing a substrate; providing a precursor composition comprising oneor more complexes of Formula I with the proviso that L is notcyclopentadienyl when Y is CO (particularly, if a hydrogen reaction gasis provided); and forming a rhodium-containing layer from the precursorcomposition on a surface of the substrate.

Preferred embodiments of the methods of the present invention involvethe use of one or more chemical vapor deposition techniques, althoughthis is not necessarily required. That is, for certain embodiments,spin-on coating, dip coating, etc., can be used.

Methods of the present invention are particularly well suited forforming layers on a surface of a semiconductor substrate or substrateassembly, such as a silicon wafer, with or without layers or structuresformed thereon, used in forming integrated circuits. It is to beunderstood that methods of the present invention are not limited todeposition on silicon wafers; rather, other types of wafers (e.g.,gallium arsenide wafers, etc.) can be used as well. Also, for certainembodiments the methods of the present invention can be used insilicon-on-insulator technology. Furthermore, substrates other thansemiconductor substrates or substrate assemblies can be used in methodsof the present invention. These include, for example, fibers, wires,etc. If the substrate is a semiconductor substrate or substrateassembly, the layers can be formed directly on the lowest semiconductorsurface of the substrate, or they can be formed on any of a variety ofthe layers (i.e., surfaces) as in a patterned wafer, for example. Thus,the term “semiconductor substrate” refers to the base semiconductorlayer, e.g., the lowest layer of silicon material in a wafer or asilicon layer deposited on another material such as silicon on sapphire.The term “semiconductor substrate assembly” refers to the semiconductorsubstrate having one or more layers or structures formed thereon.

A chemical vapor deposition system is also provided. The system includesa deposition chamber having a substrate positioned therein; a vesselcontaining a precursor composition comprising one or more complexes ofFormula I as described above; a source of an inert carrier gas fortransferring the precursor composition to the chemical vapor depositionchamber; and a source of a nonhydrogen reaction gas.

The present invention also provides platinum-rhodium (Pt—Rh) alloybarrier layers and methods for fabricating capacitors and other devicescontaining such barrier layers in order to protect cell dielectrics,such as Ta₂O₅, SrTiO₃ (“ST”), (Ba,Sr)TiO₃ (“BST”), Pb(Z,Ti)O₃ (“PZT”),SrBi₂Ta₂O₉ (“SBT”) and Ba(Zr,Ti)O₃ (“BZT”), against dielectricdegradation through thermal effects and interaction with surroundingmaterials.

The chemical vapor deposited Pt—Rh co-deposited alloy layers of theinvention provide excellent barrier protection, conductivity ascapacitor electrodes, and conformality, and so may be employed either ascapacitor electrodes, or as separate barrier layers formed adjacent toconventional capacitor electrodes, either atop these electrodes orinterposed between the electrode and the capacitor dielectric.Preferably, the CVD Pt—Rh alloy layer according to the inventioncomprises a thin barrier layer between a cell dielectric and anunderlying polysilicon (poly) plug or drain in a DRAM cell array, aswell as acting as a lower electrode. The term “CVD platinum-rhodiumalloy” herein means a material layer containing platinum and rhodium inthe compositional ranges and having the characteristic high degree ofconformality described herein.

The present invention also provides a co-deposition method for formingCVD Pt—Rh barrier films using a platinum precursor composition, arhodium precursor composition, and reaction gases for causing chemicalvapor co-deposition of a Pt—Rh alloy in a CVD reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional view taken along a portion of asemiconductor wafer at an early processing step according to oneembodiment of the present invention.

FIG. 2 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 1.

FIG. 3 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 2.

FIG. 4 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 3.

FIG. 5 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 4.

FIG. 6 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 5.

FIG. 7 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 6.

FIG. 8 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 7.

FIG. 9 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 8.

FIG. 10 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 9.

FIG. 11 is a diagrammatic cross-sectional view of a portion of asemiconductor wafer at a processing step subsequent to that shown inFIG. 10.

FIG. 12 is a schematic of a chemical vapor co-deposition system suitablefor use in the method of the present invention.

FIG. 13 shows an x-ray photoelectron spectroscopy (XPS) depth profile ofco-deposited CVD Pt—Rh layer after rapid thermal oxidation (RTO) at 750°C. for 60 seconds.

FIG. 14 shows an XPS montage display of the Si 2p photoelectron peak forVD co-deposited Pt—Rh layer after RTO at 750° C.

FIG. 15 shows the XPS profile of pure rhodium after RTO at 850° C.,indicating a layer composed of rhodium oxide.

FIG. 16 shows the XPS spectra of the Si 2p peak from pure rhodium afterRTO at 850° C.

FIG. 17 is a scanning electron microscope (SEM) image of a co-depositedPt—Rh layer on BPSG in a 0.35 diameter contact.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides methods of forming a rhodium-containinglayer, preferably an electrically conductive rhodium-containing layer,(e.g., pure rhodium, rhodium oxide, rhodium sulfide, rhodium selenide,rhodium nitride, or alloys of rhodium, particularly rhodium-platinumalloys, etc.). Specifically, the present invention is directed tomethods of manufacturing a semiconductor device, particularly aferroelectric device, having a rhodium-containing layer. Therhodium-containing layers formed are preferably conductive and can beused as barrier layers between the dielectric material and the siliconsubstrate in memory devices, such as ferroelectric memories, or as theplate (i.e., electrode) itself in the capacitors, for example. Becausethey are generally unreactive, such layers are also suitable for use inoptics applications as a reflective coating or as a high temperatureoxidation barrier on carbon composites, for example. They can bedeposited in a wide variety of thicknesses, depending on the desireduse.

The present invention provides methods of forming a metal-containinglayer using one or more rhodium complexes. These rhodium complexes aretypically mononuclear (i.e., monomers in that they contain one metal permolecule), although they can be in the form of weakly bound dimers(i.e., dimers containing two monomers weakly bonded together throughhydrogen or dative bonds). Herein, such monomers and weakly bound dimersare shown as mononuclear complexes.

An example of a fabrication process for a capacitor according to oneembodiment of the present invention is described below. It is to beunderstood, however, that this process is only one example of manypossible configurations and processes utilizing the rhodium-containinglayers (e.g., Pt—Rh barriers or electrodes) of the invention. Forexample, in the process described below, a Pt—Rh alloy material isutilized as a barrier below the bottom electrode of a capacitor.Alternatively, the top electrode may also include a Pt—Rh alloy barriermaterial.

Furthermore, doped poly or other conventional electrode materials may beprovided with a Pt—Rh layer atop the electrode, between the electrodeand the dielectric, in both locations, or the Pt—Rh alloy materialitself may form one or both electrodes in lieu of conventional electrodematerials. In addition, in the process described below the bit line isformed over the capacitor. A buried bit-line process could also be used.As another example, the plugs under the capacitors formed by thefollowing process could be eliminated. Also, dry or wet etching could beused rather than chemical mechanical polishing. The invention is notintended to be limited by the particular process described below.

Referring to FIG. 1, a semiconductor wafer fragment at an earlyprocessing step is indicated generally by reference numeral 100. Thesemiconductor wafer 100 is comprised of a bulk silicon substrate 112with field isolation oxide regions 114 and active areas 116, 118, 120.Word lines 122, 124, 126, 128 have been constructed on the wafer 100 ina conventional manner. Each word line consists of a lower gate oxide130, a lower poly layer 132, a higher conductivity silicide layer 134and an insulating silicon nitride cap 136. Each word line has also beenprovided with insulating spacers 138, also of silicon nitride.

Two FETs are depicted in FIG. 1. One FET is comprised of two activeareas (source/drain) 116, 118 and one word line (gate) 124. The secondFET is comprised of two active areas (source/drain) 118, 120 and asecond word line (gate) 126. The active area 118 common to both FETs isthe active area over which a bit line contact will be formed.

Referring to FIG. 2, a thin film 140 of nitride or TEOS is provided atopthe wafer 100. Next a layer of insulating material 142 is deposited. Theinsulating material preferably consists of borophosphosilicate glass(BPSG). The insulating layer 142 is subsequently planarized bychemical-mechanical polishing (CMP).

Referring to FIG. 3, a bit line contact opening 144 and capacitoropenings 146 have been formed through the insulating layer 142. Theopenings 144, 146 are formed through the insulating layer 142 byphotomasking and dry chemical etching the BPSG relative to the thinnitride or TEOS layer 140. Referring now to FIG. 4, a layer 150 ofconductive material is deposited to provide conductive material withinthe bit line contact opening 144 and capacitor openings 146. Theconductive layer 150 is in contact with the active areas 116, 118, 120.An example of the material used to form layer 150 is in situ arsenic orphosphorous doped poly. Referring now to FIG. 5, the conductive layer150 is etched away to the point that the only remaining material formsplugs 150 over the active areas 116, 118, 120.

Referring now to FIG. 6, a thin barrier layer 151 of a Pt—Rh alloy isformed as a barrier layer atop conductive layer 150. Barrier layer 151is co-deposited by CVD to form a conformal layer which protects thesubsequently deposited capacitor dielectric against diffusion fromunderlying plug 150 and other surrounding materials. Perhaps moreimportantly for some applications of the invention, barrier layer 151also protects the underlying plug 150 from diffusion of oxygen from thecapacitor dielectric. Chemical vapor deposition techniques are desiredbecause they are more suitable for deposition on semiconductorsubstrates or substrate assemblies, particularly in contact openingswhich are extremely small and require conformally filled layers ofmetal.

The co-deposition process includes the use of separate platinum andrhodium precursors for CVD. Any platinum and rhodium complexes suitablefor deposition via CVD may be used in the process of the invention. Therhodium precursor (whether for the preferred Pt—Rh co-deposition processor for other deposition processes described herein) is preferably of thefollowing formula, which is shown as a monomer, although weakly bounddimers are also possible:L_(y)RhY_(z),  (Formula 1)wherein: each L group is independently a neutral or anionic ligand; eachY group is independently a pi bonding ligand selected from the group ofCO, NO, CN, CS, N₂, PX₃, PR₃, P(OR)₃, AsX₃, AsR₃, As(OR)₃, SbX₃, SbR₃,Sb(OR)₃, NH_(x)R_(3-x), CNR, and RCN, wherein R is an organic group andX is a halide; y=1 to 4 (preferably, 1); z=0 to 4 (preferably, 1 to 4,more preferably, 2 or 3, and most preferably, 2); and x=0 to 3.

A particularly preferred rhodium precursor, particularly for thepreparation of Pt—Rh alloys, is a rhodium complex as shown in FormulaII:CpRh(CO)₂  (Formula II)where Cp is cyclopentadienyl.

The platinum precursor is preferably a platinum complex as shown inFormula III:MeCpPt(Me)₃  (Formula III)where Me is a methyl group and Cp is cyclopentadienyl. Other platinumcomplexes that can be used in addition or in place of the complex ofFormula III include, for example, Pt(CO)₂Cl₂, Pt(CH₃)₂[(CH₃)NC],(COD)Pt(CH₃)₂, (COD)Pt(CH₃)Cl, (C₅H₅)Pt(CH₃)(CO), (acac)(Pt)(CH₃)₃,wherein COD=1,5 cycloctadiene and acac=acetylacetonate.

For certain embodiments, the precursor compositions may be used in therange of from about 0.5% to 99.5% rhodium precursor, more preferablyabout 2% to 10% rhodium precursor, and most preferably, about 5% FormulaII (Rh) and 95% Formula III (Pt).

In Formula I above, each L ligand is a neutral or anionic ligand, whichcan include pi bonding ligands. Preferably, L is selected from the groupof dialkyl- and trialkyl-amines, polyamines (e.g.,N,N,N′N′N″-pentamethyldiethylenetriamine, diethylenetriamine),trialkylphosphines, trialkylphosphites, ethers (including linear,branched, and cyclic ethers and polyethers), unsubstituted orfluoro-substituted linear, branched, and cyclic (alicyclic) alkyls,substituted or unsubstituted linear, branched, or cyclic (alicyclic)alkenes (including monoenes, dienes, trienes, bicyclic alkenes, andpolyenes, such as cyclopentadiene (Cp), cyclooctadiene, benzene,toluene, and xylene), substituted or unsubstituted linear, branched, andcyclic (alicyclic) alkynes, alkoxy, groups (e.g., methoxy, ethoxy,isopropoxy), allyls, carboxylates, diketonates, thiolates, halides,substituted silanes (including alkoxy substituted silanes, alkylsubstituted silanes, alkenyl substituted silanes), as well as oxo,nitrile, isonitrile, cyano, and carbonyl ligands. Various combinationsof such L groups can be present in a molecule. Preferably, at least twodifferent ligands are present in each complex. More preferably, L is nota cyclopentadienyl ligand when Y is a carbonyl ligand in the presence ofa hydrogen reaction gas. Most preferably, L is a cyclopentadienyl ligandwhen Y is a carbonyl ligand in the presence of an oxidizing reactiongas.

Preferably, each R group in the complexes of Formula I is a (C₁-C₈)organic group. More preferably, each R group is a (C₁-C₅) organic group.Most preferably, each R group is a (C₁-C₄) alkyl moiety.

As used herein, the term “organic group” means a hydrocarbon group (withoptional elements other than carbon and hydrogen, such as oxygen,nitrogen, sulfur, and silicon) that is classified as an aliphatic group,cyclic group, or combination of aliphatic and cyclic groups (e.g.,alkaryl and aralkyl groups). In the context of the present invention,the organic groups are those that do not interfere with the formation ofa metal-containing layer. Preferably, they are of a type and size thatdo not interfere with the formation of a metal-containing layer usingchemical vapor deposition techniques. The term “aliphatic group” means asaturated or unsaturated linear or branched hydrocarbon group. This termis used to encompass alkyl, alkenyl, and alkynyl groups, for example.The term “alkyl group” means a saturated linear or branched hydrocarbongroup including, for example, methyl, ethyl, isopropyl, t-butyl, heptyl,dodecyl, octadecyl, amyl, 2-ethylhexyl, and the like. The term “alkenylgroup” means an unsaturated, linear or branched hydrocarbon group withone or more carbon-carbon double bonds, such as a vinyl group. The term“alkynyl group” means an unsaturated, linear or branched hydrocarbongroup with one or more carbon-carbon triple bonds. The term “cyclicgroup” means a closed ring hydrocarbon group that is classified as analicyclic group, aromatic group, or heterocyclic group. The term“alicyclic group” means a cyclic hydrocarbon group (such as a cyclicalkyl) having properties resembling those of aliphatic groups. The term“aromatic group” or “aryl group” means a mono- or polynuclear aromatichydrocarbon group. The term “heterocyclic group” means a closed ringhydrocarbon in which one or more of the atoms in the ring is an elementother than carbon (e.g., nitrogen, oxygen, sulfur, etc.).

Substitution is anticipated on the organic groups of the complexes ofthe present invention. As a means of simplifying the discussion andrecitation of certain terminology used throughout this application, theterms “group” and “moiety” are used to differentiate between chemicalspecies that allow for substitution or that may be substituted and thosethat do not allow or may not be so substituted. Thus, when the term“group” is used to describe a chemical substituent, the describedchemical material includes the unsubstituted group and that group withO, N, Si, or S atoms, for example, in the chain (as in an alkoxy group)as well as carbonyl groups or other conventional substitution. Where theterm “moiety” is used to describe a chemical compound or substituent,only an unsubstituted chemical material is intended to be included. Forexample, the phrase “alkyl group” is intended to include not only pureopen chain saturated hydrocarbon alkyl substituents, such as methyl,ethyl, propyl, t-butyl, and the like, but also alkyl substituentsbearing further substituents known in the art, such as hydroxy, alkoxy,alkylsulfonyl, halogen atoms, cyano, nitro, amino, carboxyl, etc. Thus,“alkyl group” includes ether groups, haloalkyls, nitroalkyls,carboxyalkyls, hydroxyalkyls, sulfoalkyls, etc. On the other hand, thephrase “alkyl moiety” is limited to the inclusion of only pure openchain saturated hydrocarbon alkyl substituents, such as methyl, ethyl,propyl, t-butyl, and the like.

A preferred class of complexes of Formula I include (RC₅H₄)Rh(CO)₂,where R represents one or more substituents such as methyl, ethyl,vinyl, etc., on the cyclopentadienyl group. This class of complexes ofFormula I is particularly advantageous because they are highly volatilecompounds and suitable for CVD techniques.

Methods of the present invention can be used to deposit ametal-containing layer, preferably a metal or metal alloy layer (e.g.,Pt—Rh alloy), on a variety of substrates, such as a semiconductor wafer(e.g., silicon wafer, gallium arsenide wafer, etc.), glass plate, etc.,and on a variety of surfaces of the substrates, whether it be directlyon the substrate itself or on a layer of material deposited on thesubstrate as in a semiconductor substrate assembly. The layer isdeposited upon decomposition (typically, thermal decomposition) of acomplex of Formula I, preferably one that is either a volatile liquid, asublimable solid, or a solid that is soluble in a suitable solvent thatis not detrimental to the substrate, other layers thereon, etc.Preferably, however, solvents are not used; rather, the transition metalcomplexes are liquid and used neat. Methods of the present inventionpreferably utilize vapor deposition techniques, such as flashvaporization, bubbling, etc.

A typical chemical vapor deposition (CVD) system that can be used toperform the process of the present invention is shown in FIG. 12. Thesystem includes an enclosed chemical vapor deposition chamber 110, whichmay be a cold wall-type CVD reactor. The CVD process may be carried outat pressures of from atmospheric pressure down to about 10⁻³ torr, andpreferably from about 10 torr to about 0.1 torr. A vacuum may be createdin chamber 110 using turbo pump 112 and backing pump 114, or simply adry backing pump.

One or more substrates 116 (e.g., semiconductor substrates or substrateassemblies) are positioned in chamber 110. A constant nominaltemperature is established for the substrate, preferably at atemperature of about 50° C. to about 600° C. More preferably, thetemperature is about 50° C. to about 400° C. for certain embodiments,and for other embodiments (e.g., the preparation of Pt—Rh alloys) it isabout 200° C. to about 500° C. Substrate 116 may be heated, for example,by an electrical resistance heater 118 on which substrate 116 ismounted. Other known methods of heating the substrate may also beutilized. The term “substrate” herein shall be understood to mean one ormore semiconductive layers or structures which may include active oroperable portions of semiconductor devices.

In this process, the platinum precursor composition 140, which containsone or more complexes of, for example, Formula III (and/or other metalor metalloid complexes), is stored in liquid form (a neat liquid at roomtemperature or at an elevated temperature if solid at room temperature)in vessel 142. Vessel 142 is preferably maintained at a temperatureabove about 0° C., more above about 30° C., and most preferably aboveabout 33° C. A source 144 of a suitable inert gas is pumped into vessel142 and bubbled through the neat liquid (i.e., without solvent) pickingup the precursor composition and carrying it into chamber 110 throughline 145 and gas distributor 146. Additional inert carrier gas orreaction gas may be supplied from source 148 as needed to provide thedesired concentration of precursor composition and regulate theuniformity of the deposition across the surface of substrate 116. Asshown, a series of valves 150-155 are opened and closed as required.

The rhodium precursor composition 240, which contains one or morecomplexes of, for example, Formula I, and preferably, Formula II (and/orother metal or metalloid complexes, such as MeCpRh(CO)₂), is stored inliquid form (a neat liquid at room temperature or at an elevatedtemperature if solid at room temperature) in vessel 242. The temperaturein vessel 242 is preferably above about −20° C., and more preferablyabove about 5° C. or more. A source 244 of a suitable inert gas ispumped into vessel 242 and bubbled through the neat liquid (i.e.,without solvent) picking up the precursor composition and carrying itinto chamber 110 through line 245 and gas distributor 146. Additionalinert carrier gas or reaction gas may be supplied from source 248 asneeded to provide the desired concentration of precursor composition andregulate the uniformity of the deposition across the surface ofsubstrate 116. As shown, a series of valves 154, and 250-254 are openedand closed as required.

Generally, the precursor compositions are directed into the CVD chamber110 using an inert carrier gas, at a flow rate of about 1 sccm (standardcubic centimeters per minute) to about 1000 sccm. The respective flowrates of platinum and rhodium precursors and carrier gases from vessels142 and 242, respectively, are varied to provide the desired ratio of Ptto Rh in the as co-deposited layer. The semiconductor substrate istypically exposed to the precursor compositions at a pressure of about0.001 torr to about 100 torr for a time of about 0.01 minute to about100 minutes. In chamber 110, the precursor compositions will form anabsorbed layer on the surface of the substrate 116. As the co-depositionrate is temperature dependent, increasing the temperature of thesubstrate will increase the rate of co-deposition. Typical co-depositionrates are about 10 Angstroms/minute to about 1000 Angstroms/minute. Thecarrier gases containing the precursor compositions are terminated byclosing valves 153 and 253.

In an alternative process, one or more solutions of one or more platinumand rhodium precursor compositions (and/or other metal or metalloidcomplexes) are stored in vessels and transferred to a mixing manifoldusing pumps. The resultant precursor composition mixture is thentransferred to a vaporizer, to volatilize the precursor compositionmixture. A source of a suitable inert gas is pumped into the vaporizerfor carrying the volatilized precursor composition mixture into chamber110. Reaction gas is supplied as needed.

Alternatives to such methods include an approach wherein the precursorcomposition is heated and vapors are drawn off and controlled by a vapormass flow controller, and a pulsed liquid injection method as describedin “Metalorganic Chemical Vapor Deposition By Pulsed Liquid InjectionUsing An Ultrasonic Nozzle: Titanium Dioxide on Sapphire from Titanium(IV) Isopropoxide,” by Versteeg, et al., Journal of the American CeramicSociety, 78, 2763-2768 (1995). The complexes of Formula I are alsoparticularly well suited for use with vapor deposition systems, asdescribed in copending application U.S. Ser. No. 08/720,710 entitled“Method and Apparatus for Vaporizing Liquid Precursor compositions andSystem for Using Same,” filed on Oct. 2, 1996. Generally, one methoddescribed therein involves the vaporization of a precursor compositionin liquid form (neat or solution). In a first stage, the precursorcomposition is atomized or nebulized generating high surface areamicrodroplets or mist. In a second stage, the constituents of themicrodroplets or mist are vaporized by intimate mixture of the heatedcarrier gas. This two stage vaporization approach provides areproducible delivery for precursor compositions (either in the form ofa neat liquid or solid dissolved in a liquid medium) and providesreasonable growth rates, particularly in device applications with smalldimensions.

Although a specific vapor deposition process is described by referenceto FIG. 12, methods of the present invention are not limited to beingused with the specific vapor deposition systems shown. Various CVDprocess chambers or reaction chambers can be used, including hot wall orcold wall reactors, atmospheric or reduced pressure reactors, as well asplasma enhanced reactors. Furthermore, methods of the present inventionare not limited to any specific vapor deposition techniques.

Various combinations of carrier gases and/or reaction gases can be usedin certain methods of the present invention. They can be introduced intothe chemical vapor deposition chamber in a variety of manners, such asdirectly into vaporization chamber or in combination with one or more ofthe precursor compositions.

The Pt and Rh precursors according to the invention are preferablyneutral complexes and may be liquids or solids at room temperature.Typically, they are liquids. If solids, they should be sufficientlysoluble in an organic solvent to allow for vaporization, can bevaporized from the solid state, or have melting temperatures below theirdecomposition temperatures. The precursors are suitable for use inchemical vapor deposition techniques, such as flash vaporizationtechniques, bubbler techniques, and microdroplet techniques. Thepreferred precursors described herein are particularly suitable for lowtemperature CVD, e.g., deposition techniques involving temperatures ofabout 250° C.

The precursor composition can be vaporized in the presence of an inertcarrier gas and/or a reaction gas (i.e., reacting gas) to form arelatively pure rhodium layer, a rhodium alloy layer, or otherrhodium-containing layer. The inert carrier gas is typically selectedfrom the group consisting of nitrogen, helium, argon, and mixturesthereof. In the context of the present invention, an inert carrier gasis one that is generally unreactive with the complexes described hereinand does not interfere with the formation of a rhodium-containing layer(e.g., Pt—Rh film). The reaction gas can be selected from a wide varietyof gases reactive with the complexes described herein, at least at asurface under the conditions of chemical vapor deposition. Examples ofreaction gases include hydrogen and nonhydrogen gases. As used herein, anonhydrogen reaction gas is one that does not include dihydrogen.Preferably, the reaction gas is a nonhydrogen gas. Examples include,oxidizing gases selected from the group of O₂, O₃, SO₃, H₂O, H₂O₂,nitrogen oxides, organic peroxides, RuO₄, and combinations thereof;reducing gases selected from the group of NH₃, N₂H₄, and combinationsthereof; and gases selected from the group of SiH₄, Si₂H₆, H₂S, H₂Se,H₂Te, and combinations thereof. For certain preferred embodiments, thereacting gas is selected from the group consisting of organic peroxides,O₂, O₃, NO, N₂O, SO, H₂, NH₃, and H₂O₂. Various combinations of carriergases and/or reaction gases can be used in the methods of the presentinvention to form rhodium-containing layers. Thus, therhodium-containing layer can include an oxide, nitride, ect., orcombinations thereof. Such metal-containing layers can also be formed bysubjecting a relatively pure metal layer to subsequent processing toform other metal-containing layers. Significantly, an oxidizing gas canbe used to form a relatively pure rhodium layer without oxygen or carbonincorporation.

Various complexes can be used in a precursor composition. Thus, as usedherein, a “precursor composition” refers to a liquid or solid thatincludes one or more complexes of the formulas described hereinoptionally mixed with one or more complexes of formulas other than thoseof Formulas I, II, and III. The precursor compositions can also includeone or more organic solvents suitable for use in a chemical vapordeposition system, as well as other additives, such as free ligands,that assist in the vaporization of the desired compounds.

The solvents that are suitable for this application can be one or moreof the following: saturated or unsaturated linear, branched, or cyclicaliphatic (alicyclic) hydrocarbons (C₃-C₂₀, and preferably C₅-C₁₀),aromatic hydrocarbons (C₅-C₂₀, and preferably C₅-C₁₀), halogenatedhydrocarbons, silylated hydrocarbons such as alkylsilanes,alkylsilicates, ethers, polyethers, thioethers, esters, lactones,ammonia, amides, amines (aliphatic or aromatic, primary, secondary, ortertiary), polyamines, nitrites, cyanates, isocyanates, thiocyanates,silicone oils, aldehydes, ketones, diketones, carboxylic acids, water,alcohols, thiols, or compounds containing combinations of any of theabove or mixtures of one or more of the above. It should be noted thatsome precursor complexes are sensitive to reactions with proticsolvents, and examples of these noted above may not be ideal, dependingon the nature of the precursor complex. The complexes are also generallycompatible with each other, so that mixtures of variable quantities ofthe complexes will not interact to significantly change their physicalproperties.

One preferred method of the present invention involves vaporizing(preferably, by a bubbling technique) a precursor composition thatincludes one or more rhodium complexes. Also, the precursor compositioncan include complexes containing other metals or metalloids,particularly if flash vaporization is the vaporizing technique.

The complexes described herein can be used in precursor compositions forchemical vapor deposition. Alternatively, certain complexes describedherein can be used in other deposition techniques, such as spin-oncoating, dip coating, and the like. Typically, those complexescontaining R groups with a low number of carbon atoms (e.g., 1-4 carbonatoms per R group) are suitable for use with vapor depositiontechniques. Those complexes containing R groups with a higher number ofcarbon atoms (e.g., 5-12 carbon atoms per R group) are generallysuitable for spin-on or dip coating. Preferably, however, chemical vapordeposition techniques are desired because they are more suitable fordeposition on semiconductor substrates or substrate assemblies,particularly in contact openings which are extremely small and requireconformally filled layers of metal.

For the preparation of rhodium alloy layers, at least one complex ofFormula I can be combined with another complex in a precursorcomposition or they can be provided in separate bubblers or vaporizers,for example (e.g., MeCpRh(CO)₂ and CyclohexadieneRu(CO)₃ for a Rh/Rualloy).

The precursor compositions for use in the present invention can beprepared by a variety of methods. For example, rhodium precursors can beprepared by reacting NaCp with [RhCl(CO)₂]₂. In addition, the precursorsfor platinum co-deposition may be purchased from, e.g., Strem ChemicalCo.

Following chemical vapor co-deposition of barrier layer 151, a layer 152of conductive material that will eventually form one of the electrodesof the capacitor is deposited at a thickness such that the capacitoropenings 146 are not closed off. Referring to FIG. 7, the layer 152 maybe formed of various refractive metals, conductive metal oxides, metalnitrides, noble metals and may include, such as, Pt, Rh, Ir, Ru, Os, Pd,IrO₂, RhO₂, RuO₂, Ta, TiN, TaN, Ti and others. The conductive layer 152is in electrical contact with the previously formed plugs 150 or, aspreviously mentioned, the Pt—Rh layer will itself be the lowerelectrode.

Referring to FIG. 8, the portion of the conductive layer 152 above thetop of the BPSG layer 142 is removed through a planarized etchingprocess, thereby electrically isolating the portions of layer 152remaining in the bit line contact opening 144 and capacitor openings146. Referring now to FIG. 9, a capacitor dielectric layer 154 isprovided over conductive layer 152 and capacitor openings 146.

Dielectric layer 154 is deposited with a thickness such that theopenings 146 are again not completely filled. Dielectric layer 154 maycomprise tantalum pentoxide (Ta₂O₅). Other suitable dielectric materialssuch as Strontium Titanate (ST), Barium Strontium Titanate (BST), LeadZirconium Titanate (PZT), Strontium Bismuth Tantalate (SBT) and BismuthZirconium Titanate (BZT) may also be used. Dielectric layer 154 may bedeposited by a low-pressure CVD process using Ta(OC₂H₅)₅ and O₂ at about430° C., and may be subsequently annealed in order to reduce leakagecurrent characteristics.

A second conductive electrode layer 156 is then deposited by CVD overthe dielectric layer 154, again at a thickness which less thancompletely fills the capacitor openings 146. The second conductive layer156 may be comprised of TiN, Pt, or other conventional electrodematerials, such as many of those previously described for use asconductive layer 152. In addition to serving as the top electrode orsecond plate of the capacitor, the second conductive layer 156 alsoforms the interconnection lines between the second plates of allcapacitors.

Referring to FIG. 10, the second conductive layer 156 and underlyingcapacitor dielectric layer 154 are patterned and etched such that theremaining portions of each group of the first conductive layer 152,capacitor dielectric layer 154, and second conductive layer 156 over thebit line contact opening 144 and capacitor openings 146 are electricallyisolated from each other. In this manner, each of the active areas 116,118, 120 are also electrically isolated (without the influence of thegate). Furthermore, at least a portion of the barrier layer 151 andfirst conductive layer 152 in contact with the plug 150 over the bitline active area 118 is are outwardly exposed.

Referring now to FIG. 11, a bit line insulating layer 158 is providedover the second conductive layer 156. The bit line insulating layer 158is preferably comprised of BPSG. The BPSG is typically reflowed byconventional techniques, i.e., heating to about 800° C. Other insulatinglayers such as PSG, or other compositions of doped SiO₂ may similarly beemployed as the insulating layer 158.

A bit line contact opening 160 is patterned through the bit lineinsulating layer 158 such that the barrier layer 151 above conductiveplug 150 is once again outwardly exposed. Then a bit line contactmaterial is provided in the bit line contact opening 160 such that thebit line contact material is in electrical contact with the outwardlyexposed portion of the barrier layer 151 above conductive plug 150.Thus, the plug 150 over the active area 118 common to both FETs acts asa bit line contact. The DRAM array and associated circuitry may then becompleted by a variety of well established techniques, such asmetalization, and attachment to peripheral circuitry.

The advantages of co-depositing Rh with Pt for the barrier layer 151will now be discussed with references to FIGS. 13-17. FIG. 13 shows anXPS depth profile of a Pt—Rh alloy, produced by CVD co-deposition of Ptand Rh, after annealing in oxygen at 750° C. for 60 seconds. The rhodiumconcentration in the Ph—Rh layer is about 6%. FIG. 14 shows an XPSmontage plot of the Si in the layer of FIG. 13, indicating the lack ofoxygen at the Pt—Rh interface, and no Si at the surface.

FIG. 15 shows, for comparison, an XPS depth profile of a pure Rh layer(after RTO) for comparison of oxygen barrier properties. The surface hadrhodium oxide present. The interface with silicon was composed ofrhodium oxide, silicon oxide and rhodium silicide. FIG. 16 shows the XPSspectra of the Si2p peak at the Rh/Si interface on the layer of FIG. 15,indicating significant levels of SiO₂. Tables 1 and 2 show thecomposition of the layer at the rhodium/silicon interface. This datashows that after annealing in oxygen, Rh is present primarily as anoxide of rhodium, and silicon is present as atomic Si (58%) and SiO₂(42%). Thus, the pure rhodium is at least partially permeable to oxygen,and the substrate is not passivated by the native oxide.

TABLE 1 Area Sensitivity Concentration Element cts-eV/s Factor (%) C1s19 5.588 0.06 O1s 25659 14.162 33.70 Si2p 10239 6.197 30.73 Rh3d 17423991.315 35.50

TABLE 2 Band Peak % Total No. Pos. Delta Height FWHM Gauss Area Area 2102.64 2.88 1218 2.70 54 4265 41.56 1 99.75 0.00 3448 1.56 90 5998 58.44

FIG. 17 is an SEM of CVD Pt—Rh co-deposited in a 0.35 um contact. TheSEM demonstrates the good step coverage and conformality obtained fromthe co-deposited Pt—Rh alloy according to the invention. Conformality ofthe CVD Pt—Rh alloy barrier layers of the invention, as shown in FIG.17, is about 35% step coverage on a 0.35 diameter by 2.4 micrometercontact. This level of conformality or better is characteristic of theCVD Pt—Rh alloy layers of the invention.

The Pt—Rh alloy barrier layer and electrode materials according to theinvention also have excellent conductivity, and therefor reducedepletion effects and enhance frequency response. The materials possessexcellent barrier properties for protection of cell dielectrics andsubstrate during oxidation/recrystallization steps for dielectrics andduring BPGS reflow and other high temperature steps after capacitorformation. In addition, the Pt—Rh alloy barriers according to theinvention also substantially prevent diffusion to protect celldielectrics from interaction with Si and other surrounding materialswhich may degrade the dielectric materials or produce an additional SiO₂dielectric layer; the series capacitance of SiO₂ would drasticallyreduce overall cell capacitance. Thus, the barriers/electrodes of theinvention are not limited to use as barrier layers for bottomelectrodes, but may also be employed both as top and bottom electrodes,and as additional barrier layers applied to any other top and/or bottomelectrodes.

In addition, the use of the platinum and rhodium precursor compositionsand methods of forming co-deposited Pt—Rh alloy layers of the presentinvention are beneficial for a wide variety of thin film applications inintegrated circuit structures, particularly those using high dielectricmaterials. For example, such applications include capacitors such asplanar cells, trench cells (e.g., double sidewall trench capacitors),stacked cells (e.g., crown, V-cell, delta cell, multi-fingered, orcylindrical container stacked capacitors).

Although a specific vapor deposition process is described by referenceto FIG. 12, methods of the present invention are not limited to thespecific vapor deposition system shown. Various CVD process chambers orreaction chambers can be used, including hot wall or cold wall reactors,atmospheric or reduced pressure reactors, as well as plasma enhancedreactors. Furthermore, methods of the present invention are not limitedto any specific vapor deposition techniques.

Accordingly, the above description and accompanying drawings are onlyillustrative of preferred embodiments which can achieve and provide theobjects, features and advantages of the present invention. It is notintended that the invention be limited to the embodiments shown anddescribed in detail herein. The invention is only limited by the spiritand scope of the following claims. All patents, patent applications, andpublications referred to herein are incorporated herein by reference asif each were individually incorporated by reference.

1. A method for fabricating a capacitor comprising the steps of: forminga first conductive layer; forming a dielectric layer atop said firstconductive layer; forming a second conductive layer atop said dielectriclayer; wherein at least one of said first and second conductive layerscontains a CVD platinum-rhodium alloy formed from a precursorcomposition comprising one or more complexes of the formula:L_(y)RhY_(z), wherein: each L group is independently a neutral oranionic ligand: each Y group is independently a bonding ligand selectedfrom the group of CO, NO, CN, CS, N₂, PX₃, P(OR)₃, AsX₃, AsR₃, As(OR)₃,SbX₃, SbR₃, Sb(OR)₃, NH_(x)R_(3-x), CNR, and RCN, wherein R is anorganic group, X is a halide, and x=0 to 3; y=1 to 4; and z=0 to
 4. 2.The method of claim 1 wherein said first conductive layer contains a CVDplatinum-rhodium alloy.
 3. The method of claim 1 wherein said secondconductive layer contains a CVD platinum-rhodium allay.
 4. The method ofclaim 1 wherein said dielectric is selected from the group consisting oftantalum pentoxide (Ta₂O₅), Strontium Titanate (ST), Barium StrontiumTitanate (BST), Lead Zirconium Titanate (PZT), Strontium BismuthTantalate (SBT) and Bismuth Zirconium Titanate (BZT).
 5. The method ofclaim 1 wherein said at least one conductive layer that contains a CVDplatinum-rhodium alloy is formed by chemical vapor co-deposition ofplatinum and rhodium precursor compositions.
 6. The method of claim 5wherein said platinum precursor composition comprises MeCpPt (Me)₃,where Me is a methyl group and Cp is cyclopentadienyl.
 7. The method ofclaim 5 wherein said rhodium precursor composition comprises CpRh(CO)₂,where Cp is cycolopentadienyl.
 8. The method of claim 5 wherein saidchemical vapor co-deposition is conducted in a reaction chamber at atemperature in the range of about 100 to about 600° C.
 9. The method ofclaim 5 wherein said chemical vapor co-deposition is conducted in areaction chamber at a temperature in the range of about 200 to about500° C.
 10. The method of claim 5 wherein said chemical vaporco-deposition is conducted in a reaction chamber at a pressure in therange of about 0.1 torr to about 10 torr.
 11. The method of claim 5wherein said chemical vapor co-deposition is conducted by depositing aratio of rhodium to platinum in the range of about 0.5 to about 99.5%rhodium.
 12. The method of claim 5 wherein said chemical vaporco-deposition is conducted by depositing a ratio of rhodium to platinumin the range of about 2% to about 10% rhodium.
 13. The method of claim 5wherein said chemical vapor co-deposition is conducted by depositing aratio of rhodium to platinum of about 5%.
 14. The method of claim 5wherein said vapor co-deposition is conducted using a reacting gascomprising a gas selected from the group consisting of organicperoxides, O₂, O₃, NO, N₂O, SO₃, H₂, NH₃, and H₂O₂.
 15. A method forfabricating a capacitor comprising the steps of: forming a firstconductive layer; forming a dielectric layer atop said first conductivelayer; forming a second conductive layer atop said dielectric layer; andforming a conductive barrier layer containing a CVD platinum-rhodiumalloy formed from a precursor composition comprising one or morecomplexes of the formula:L_(y)RhY_(z); wherein: each L group is independently a neutral oranionic ligand; each Y group is independently a pi bonding ligandselected from the of group CO, NO, CN, CS, H₂, PX₃, PR₃, P(OR)₃, AsX₃,AsR₃, As(OR)₃, SbX₃, SbR₃, Sb(OR)₃, NH_(x)R_(3-x), CNR, and RCN, whereinR is an organic group, X is a halide, and x=0 to 3; y=1 to 4; and z=0 to4.
 16. The method of claim 15 wherein said first conductive layer isinterposed between said barrier layer and said dielectric.
 17. Themethod of claim 15 wherein said second conductive layer is interposedbetween said barrier and said dielectric.
 18. The method of claim 15wherein said dieleciric is selected from the group consisting oftantalum pentoxide (Ta₂O₅), Strontium Titanate (ST), Barium StrontiumTitanate (BST), Lead Zirconium Titanate (PZT), Strontium BismuthTantalate (SBT) and Bismuth Zirconium Titanate (BZT).
 19. The method ofclaim 15 wherein said conductive barrier layer is formed by chemicalvapor co-deposition of platinum and rhodium precursor compositions. 20.The method of claim 19 wherein said platinum precursor compositioncomprises MeCpPt (Me)₃, where Me is a methyl group and Cp iscyclopentadienyl.
 21. The method of claim 19 wherein said rhodiumprecursor composition is selected from the group consisting of CpRh(CO)₂and MeCpRh(CO)₂, where Cp is cyclopentadienyl.
 22. The method of claim19 wherein said chemical vapor co-deposition is conducted in a reactionchamber at a temperature in the range of about 100 to about 600° C. 23.The method of claim 19 wherein said chemical vapor co-deposition isconducted in a reaction chamber at a temperature in the range of about200 to about 500° C.
 24. The method of claim 19 wherein said chemicalvapor co-deposition is conducted in a reaction chamber at a pressure inthe range of about 0.1 torr to about 10 torr.
 25. The method of claim 19wherein said chemical vapor co-deposition is conducted by depositing aratio of rhodium to platinum in the range of about 0.5 to about 99.5%rhodium.
 26. The method of claim 19 wherein said chemical vaporco-deposition is conducted by depositing a ratio of rhodium to platinumin the range of about 2% to about 10% rhodium.
 27. The method of claim19 wherein said chemical vapor co-deposition is conducted by depositinga ratio of rhodium to platinum of about 5%.
 28. The method of claim 19wherein said vapor co-deposition is conducted using a reacting gascomprising a gas selected from the group consisting of organicperoxides, O₂, O₃, NO, N₂O, SO₃, NH₃, H₂ and H₂O₂.